the age of Tertiary Deposits. 113 



deposits. M. Deshayes, and Mr. Lyell,* while they admit 

 the incontestably later date of the faluns and crag, than of the 

 whole Paris basin, have made of the former, two distinct for- 

 mations, from the proportional number of their fossil shells, 

 analogous to species now existing ; which, according to M. 

 Deshayes, differs greatly in each : and it has been concluded 

 from this, that they are separated from each other by some 

 one of the revolutions which have determined the formation 

 of the last great chain of mountains. The faluns, according 

 to M. Deshayes, (whose zoological results Mr. Lyell has en- 

 tirely adopted, by making them the basis of his three tertiary 

 periods, eocene, miocene, and pliocene), should contain 19 per 

 cent, of shells analogous to recent species, and should be- 

 long to the middle tertiary formation, the miocene of Mr. Ly- 

 ell ; which comprehends also the greater part of the tertiary 

 strata of the Gironde, those of Vienna, Turin, &c. The crag 

 on the contrary, containing at least 50 per cent, of species 

 analogous to the recent ones, should belong to the upper ter- 

 tiary formation, the pliocene ; to which also are referred the 

 sub-appennine hills, Sicily, and other deposits in the basin of 

 the Mediterranean, and even the littoral deposits, formed al- 

 most entirely of species now living in the neighbouring seas, 

 as those of Nice, Uddewalla, and many others. 



Now results so positive are found to be contradicted, and 

 this order set aside, at least provisionally, by the more recent 

 observations of M. Dujardin, upon the faluns ; and those of 

 Dr. Beck, upon the crag. Biassed by preconceived opinions 

 of a completely opposite nature, M. Dujardin, inclining to 

 admit analogous species, and Dr. Beck not to acknowledge 

 any ; these two naturalists arrive at results, each entirely dif- 

 ferent from those of M. Deshayes, which have been the sole 

 cause for distinguishing between the faluns and the crag. M. 

 Dujardin,f after having for a long time hesitated to admit, in 

 support of the recent age of the faluns, the close and indispu- 

 table connection which I had pointed out, between the fresh- 

 water stratum of the Loire, covered by the faluns, and the 

 Parisian freshwater stratum, has been led, by the mere exa- 

 mination of the fossil shells of the faluns, — an examination 



* Lyell, Principles of Geology, first edition. The tables of M. Deshayes, 

 published in an appendix at the end of the third volume, May, 1833. The 

 results of his important labours since published in several other works, have 

 been again brought forward by M. Deshayes, in his last memoir on the 

 temperature of the tertiary periods. (Annales des Sciences naturelles, May, 

 1836.) 



f Memoirs on the deposits in Touraine. Memoires de la Societe geolo- 

 gique de France. Vol. II. 2nd part, 1837. 



K 2 



